A dual-mode highly selective and sensitive Schiff base chemosensor for fluorescent colorimetric detection of Ni2+ and colorimetric detection of Cu2+

Abstract

In this paper, a novel flexible Schiff base chemosensor N′-(2-hydroxy-3-methoxybenzylidene)-2-(benzamido)benzohydrazide (L) has been designed, synthesised and characterised by ¹H-NMR, IR spectroscopy, ESI-MS spectrometry and single crystal XRD analysis. A significant fluorescence enhancement of L was observed only in the presence of Ni²⁺ ions with a detection limit of 3.64 μM whereas Cu²⁺ induced fluorescence quenching, although both the metals showed colorimetric responses in methanol–Tris-HCl buffer (10 mM, pH 7.2) solution (1 : 1, v/v). The single crystal structure of L–Cu²⁺ has also been determined. No major interference by the other effective background cations (Fe³⁺, Fe²⁺, Co²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺, Cr³⁺, Ag⁺, Al³⁺ and Mn²⁺) was observed even at a higher concentration of analytes. The experimental results were further supported by DFT studies. The chemosensor L can be applied to the formation of binary logical devices, recovery of contaminated water samples and living intracellular media.